Adam Rutherford is back to celebrate the 20th anniversary of one of the most ambitious and revolutionary scientific endeavours of all time - the Human Genome Project. Its scope and scale was breath-taking, set up to read every one of the 3 billion nucleotides, or letters of genetic information, contained within the DNA in every cell of the human body. It took seven years, hundreds of scientists, cost almost $3 billion and, amazingly, came in under budget and on time. Adam reflects back on that momentous time with Ewan Birney, Director of the European Bio-informatics Institute, part of the European Molecular Biology Laboratory. Twenty years ago, he was a PhD student working on the project, in the months leading up to the first draft. The Human Genome Project underpins many branches of science, from human evolution and synthetic biology to forensic genetics and ancestry testing. But a key motivation for the project was to alleviate human suffering. While the ‘cures’, hyped by the media back in 2000, were not realistic our understanding of disease has been revolutionised. Adam talks to Cancer Research UK Scientist, Dr Serena Nik-Zainal, from Cambridge University, who explains why the sequencing of the human genome has been so crucial to the diagnosis and treatment of breast cancer. The Human Genome Project is also playing a crucial role in the COVID-19 pandemic. Dr Kenneth Baillie has been treating critically ill patients at Edinburgh’s Royal Infirmary since the pandemic started. As the Lead on GenOMICC, a global collaboration on genetics and critical illness, he has joined forces with Genomics England and the NHS, to pinpoint genetic signals in these patients to help identify the best treatments. Producers: Beth Eastwood & Fiona Roberts